1. Field of the Invention
The present invention relates to a method and system for performing serial data communication between a main device and an external module connected to the main device.
2. Description of the Related Art
FIG. 1 is a block diagram illustrating a conventional multiple serial communication apparatus disclosed in Korean Patent Application No. 1998-0059854. Referring to FIG. 1, the multiple serial communication apparatus changes the use of a universal asynchronous receiver/transmitter (UART) port 11 that performs RS232 communication according to the state of a port input/output (PIO) 12 in a communication control module 10. The multiple serial communication apparatus employed in a control board of a mobile communication system recognizes the RS232 communication according to the connection state of a cable, outputs a logical LOW state of the PIO 12 of the communication control module 10, and uses the UART port 11 for RS232 communication under the control of a selector 80. However, when the multiple serial communication apparatus fails to recognize the RS232 communication according to the connection state of the cable, the apparatus may output a logical HIGH state of the PIO 12 of the communication control module 10, and use the UART port 11 for infrared communication under the control of the selector 80.
Two UART serial communication pins Rx and Tx (the UART port 11) are conventionally used to perform standardized serial communication. For example, if it is possible to connect a device A to modules B and C via RS232 communication, the modules B and C that are connected to the device A perform communication, whereas the device A merely receives data but does not determine whether the module B or C is actually connected to device A. Thus, another detection pin is needed to recognize such a connection.